Left Unilateral Neglect Research Articles

Residual rightward attentional bias after apparent recovery from right hemisphere damage: implications for a multicomponent model of neglect.

Unilateral neglect may be a multicomponent attentional disorder consisting of an initial automatic orienting of attention toward the ipsilesional side and a subsequent impairment in contralesionally reorienting attention, both of which are superimposed on a generalised reduction in attention resources. It has been hypothesised that patients' ability to reorient attention contralesionally may recover relatively quickly, but that the ipsilesional attention bias may be relatively persistent. This hypothesis was tested by consecutively examining 13 patients who had had a right hemisphere stroke, and who had left unilateral neglect. They were examined once shortly after the stroke and again 12 months later, using a battery of standard clinical and experimental tasks. Patients initially showed a strong and consistent rightward attentional bias in addition to a failure to reorient their attention leftward. After 12 months patients continued to show an abnormal ipsilesional attentional bias, though most were now able to fully reorient their attention toward the contralesional side. These results suggest that restitution of the capacity to reorient attention contralesionally may underlie the apparent recovery from clinical signs of unilateral neglect. The presence of a residual ipsilesional attentional bias in most patients, however, may, at least in part, account for the poor functional outcomes in some apparently "recovered" patients.

Reversed Perceptual Asymmetry for Faces in Left Unilateral Neglect

Twelve patients with left unilateral neglect and 12 matched controls were examined on two tests of face perception. In the chimeric faces task, subjects were required to make a judgement of happiness on pairs of photographic chimeras, while in the face-matching task, they were required to indicate which of two symmetrical face composites more closely resembled the original. Whereas controls showed a significant leftward perceptual bias on both tasks, left neglect patients showed an even stronger rightward (reversed) perceptual bias. Patients with and without left-sided visual field defects exhibited the reversed asymmetry, and the degree of perceptual bias shown by patients was not related to the severity of their symptoms as measured by standard clinical tasks. There was no relationship between the extent of rightward bias exhibited by patients or controls on the two tasks. These results contribute to our understanding of the mechanisms underlying unilateral neglect. Moreover, the tasks themselves may be employed as a simple and sensitive adjunct to the clinical assessment of this disorder.

Unilateral neglect in route description

Route description was investigated in two patients suffering from left unilateral neglect. Both had evident difficulty with left turns. This findings suggests that the topological correspondence between represented environment and representational mechanisms in the brain is not confined to frozen (picture-like) perspectives.

To see or not to see: The effects of visible and invisible cues on line bisection judgements in unilateral neglect

Patients with left unilateral neglect and matched controls were tested in two experiments to examine the effects of lateralized cues on line bisection judgements. Unlike previous studies in which letter or number cues were placed beyond the endpoint(s) of each line, we adopted a procedure which maintained the perceptual point of balance in the horizontal axis of each line. We also related the cueing task more closely to the act of bisection by requiring subjects to place a small mark in direct alignment with the endpoint(s) of each line. In the first experiment, it was found that, for controls, the presence or absence of visible lateralized cues did not differentially affect the magnitude of bisection errors. However, the magnitude of bisection errors made by neglect patients was significantly reduced (and reversed) in the presence of a visible left-sided cue, but remained well to the right of the midpoint in the absence of such cues. In a second experiment, subjects engaged in an otherwise identical cueing procedure, except that no visible marks appeared on the stimulus lines. Neither subject group was affected by the presence or absence of right-sided cues. However, the presence of left-sided cues again reduced the magnitude of bisection errors in neglect patients, but not in controls. These results indicate that the extent of the attentional bias exhibited by neglect patients can be ameliorated even in the absence of lateralized visible cues.

Study on an Evaluation Method of Attentional Deficit(First Report)

A quantitative evaluation system of attentional deficit was developed, and was tried to normal subjects and stroke patients. In patients of generalized attentional defict there were many errors or miss, and they took long response times for stimulus of all or special directions. For example, patient who showed left unilateral special neglect took longer response time for left side stimulus than right side. By experiments, it was suggested that this evaluation method was useful for measurment of an attentinal deficit.

Spatio-motor cueing in unilateral left neglect: The role of hemispace, hand and motor activation

Reported beneficial effects of left arm activation on neglect are experimentally examined. The present study of a subject with left visual neglect compared left hand finger movement with an instruction to visually anchor perception on the left arm during letter cancellation. Only the finger movements significantly reduced neglect. Another comparison was between “out of sight” finger movements of the left hand in left and right hemispace, respectively. Only left hemispace “blind” finger movements significantly reduced neglect compared to the standard condition. Thirdly, blind left finger movements in left hemispace were compared with passive visual cueing (reading a changing number) and again it was found that only the finger movements reduced neglect. Finally, right finger movements in left hemispace were compared with left finger movements in left hemispace: only the latter reduced neglect. The implications of these findings for theory and therapy of neglect are discussed.

Left Unilateral Neglect in a Preschool Child

The authors present a case of transient left hemispatial inattention following traumatic brain injury in a three-year-old child. Computed tomographic scan revealed a small right frontal and a right temporo-parietal contusion. Stimuli were developed to quantify the response difference between hemifields in this pre-literate child. Hemispatial inattention showed resolution at 19 days post-trauma and had completely resolved six months later. These findings suggest that right hemisphere systems subserve visually guided attention before six years of age.

Attentional load and visual neglect.

Ten subjects suffering from left unilateral neglect carried out a letter cancellation task under normal conditions, while counting forward, and when generating random numbers, respectively. The index of neglect increased with each of these conditions, though only the normal-random difference was statistically significant. In a second study, four left unilateral neglect subjects and four right brain-damaged controls carried out a simple reaction time task, with stimuli appearing randomly to the left and right, with and without the simultaneous performance of a secondary task (counting backward in threes from 100). The discrepancy between left versus right latencies increased significantly in the secondary task condition for two patients in the neglect group but not for the other two. None of the control group showed this effect. Theoretical implications of these findings for understanding neglect are discussed.

Unilateral Displacement in the Olfactory Sense: A Manifestation of the Unilateral Neglect Syndrome

Unilateral neglect is a syndrome primarily occurring with right hemisphere — particularly right parietal lobe—brain damage and involving the failure to respond to stimuli presented to the left side of the body and space. Unilateral displacement (a less severe manifestation of the neglect syndrome) involves the accurate identification of a stimulus, but the displacement or mislocalization of that stimulus to the opposite side of the body and space. This study investigated two major theories of unilateral neglect utilizing the primarily ipsilaterally innervated olfactory sense. The sensory theory states that unilateral neglect is due to a diminished sensory input, whereas the representational theory states that it is due to a disordered internal representation which is not dependent on sensory input. Results revealed that right hemisphere lesion patients with left unilateral neglect exhibited a significantly greater number of displacements in their left nostril on olfactory double simultaneous stimulation, consistent with the representational theory.

Reactions of patients with focal cerebral lesions to success or failure

Multiple measures were used to investigate emotional reactions to card sorting in patients with focal cerebral lesions and in matched non-brain-injured controls. Spontaneous facial expressions of patients with anterior lesions were impoverished, relative to the posterior group, on a quantitative index of facial movement. This deficit did not appear to be attributable to group differences on lesion variables, or degree of cognitive deficit. There were also indications that a “non-emotional” facial-motor deficit was not the primary cause. The marked anterior deficit for facial movement was not, however, associated with equally pronounced deficits on qualitative, self-report and heart rate indices of emotional response. Right hemisphere patients differed from left hemisphere patients on only one qualitative measure of emotional reaction, but this may have been due to the stronger negative reactions of dysphasic patients. Left unilateral neglect was not associated with reduced emotional response.

The nature of unilateral neglect in the olfactory sensory system

This study investigated two major theories of unilateral neglect utilizing the ipsilaterally innervated olfactory sense. The sensory theory states that unilateral neglect is due to a diminished or attenuated sensory input. The representational theory states that unilateral neglect is due to a disordered internal representation, which is not dependent on sensory input. Results of the study revealed that right hemisphere lesion patients with left unilateral neglect failed to respond to their left contralateral nostril on olfactory double simultaneous stimulation, consistent with the representational theory because the left nostril has no direct sensory input to the right hemisphere.

Oculomotor disorders in cortical lesions in man: The role of unilateral neglect

The saccades of 22 patients with lesions of the left (6) and right (16) hemisphere were analysed. Seven patients with a right hemispheric lesion presented a left unilateral neglect (UN) syndrome. In the first test session the saccades were performed in response to a predicted sequence of targets; in the second session the luminous stimuli were unpredicted and randomized. In patients with UN we observed the absence of saccadic response to 25% of the targets, a lengthening of the reaction time and a staircase pattern in the left hemifield. In the predicted stimulus sequence the oculomotor performance was not significantly better. Hemianopia, a defect of arousal and an altered visuospatial orientation are the most important elements that account for the alterations of oculomotor strategy in the UN syndrome.

Unilateral Neglect of Representational Space

Two patients showing left unilateral neglect were asked to describe imagined perspectives of familiar surroundings. Left-sided details were largely omitted in the descriptions. Some theoretical implications of the occurrence of unilateral neglect in representational space are briefly considered.

Changes in the symptoms of neglect induced by changing task strategy.

Six patients with left side unilateral neglect from lesions of the right cerebral hemisphere were tested with verbal and visuospatial crossing-out tasks. The symptoms of neglect were less severe with the visuospatial than with verbal tasks. We hypothesize that changes in the symptoms of neglect were produced because the tasks altered hemispheric arousal.

Auditory affective agnosia. Disturbed comprehension of affective speech.

Hughlings Jackson noted that, although some aphasic patients were unable to use propositional speech, affective speech appeared to be spared. The purpose of this experiment was to study patients with unilateral hemispheric disease in order to ascertain if there are hemispheric asymmetries in the comprehension of affective speech. Six subjects had right temporoparietal lesions (left unilateral neglect) and six subjects had left temporoparietal lesions (fluent aphasias). These subjects were presented with 32 tape recorded sentences. In 16 trials the patients were asked to judge the emotional mood of the speaker (happy, sad, angry, indifferent) and in 16 trials the patients were asked to judge the content. Line drawings containing facial expressions of the four emotions or line drawings corresponding with the four basic contents were displayed with each sentence and the patient responded by pointing. All 12 subjects made perfect scores on the content portion of the test. On the emotional portion the right hemispheric patients scored a mean of 4-17 and the left hemispheric group scored a mean 10-17. The difference between these means is significantly (P less than 0-01) and suggests that patients with right hemispheric dysfunction and neglect have a defect in the comprehension of affective speech.